Integrated strategic and tactical biomass-biofuel supply chain optimization

To ensure effective biomass feedstock provision for large-scale biofuel production, an integrated biomass supply chain optimization model was developed to minimize annual biomass-ethanol production costs by optimizing both strategic and tactical planning decisions simultaneously. The mixed integer linear programming model optimizes the activities range from biomass harvesting, packing, in-field transportation, stacking, transportation, preprocessing, and storage, to ethanol production and distribution. The numbers, locations, and capacities of facilities as well as biomass and ethanol distribution patterns are key strategic decisions; while biomass production, delivery, and operating schedules and inventory monitoring are key tactical decisions. The model was implemented to study Miscanthus-ethanol supply chain in Illinois. The base case results showed unit Miscanthus-ethanol production costs were $0.72 L-1 of ethanol. Biorefinery related costs accounts for 62% of the total costs, followed by biomass procurement costs. Sensitivity analysis showed that a 50% reduction in biomass yield would increase unit production costs by 11%. (C) 2014 Elsevier Ltd. All rights reserved

Determining optimal size reduction and densification for biomass feedstock using the BioFeed optimization model

The benefits of particle size reduction and mechanical densification of biomass feedstock for storage, transportation, and handling must be assessed in relation to the systemic costs and energy consumption incurred due to these operations. The goal of this work was to determine the optimal levels of size reduction and densification through a combination of modeling and experimental studies. Size reduction and densification data for Miscanthus and switchgrass were generated using a two-stage grinding process and the energy requirement and bulk densities for the particle sizes between 1mm and 25.4 mm were determined. Increase in bulk density through compression by a pressure of 1.2 MPa was also measured. These data were used within BioFeed, a system-level optimization model, to simulate scenarios capturing the possibilities of performing size reduction and densification at various stages of the supply chain. Simulation results assuming size reduction at farms showed that the optimal particle size range for both Miscanthus and switchgrass was 4-6 mm, with the optimal costs of $54.65 Mg-1 and$60.77 Mg-1 for Miscanthus and switchgrass, respectively. Higher hammer mill throughput and lower storage costs strongly impacted the total costs for different particle sizes. Size reduction and densification of biomass at the county-specific centralized storage and pre-processing facilities could reduce the costs by as much as $6.34 Mg-1 for Miscanthus and$20.13Mg(-1) for switchgrass over the base case. These differences provided the upper bound on the investments that could be made to set-up and operate such systems. (c) 2014 Society of Chemical Industry and John Wiley & Sons, Lt